SELECTION OF SPECIES FOR STUDY 181
Meanwhile other matters can be attended to. A certain
number of perennial plants can be chosen for study. The
particular species chosen must of course depend on what
grows in the neighbourhood. They should not be too
numerous (perhaps half a dozen), and they should all be
common plants, so far as possible characteristic of different
communities, e.g. a woodland plant like dog's mercury,
stitchwort, or wood violet, a heath plant like the ling itself,
a wayside plant like silverweed or a species of plantain,
one or two pasture plants, including a dominant grass, and
so on. To these may be added two or three annuals, prefer-
ably those whose development has been followed from the
seedling.
In a mainly agricultural region, where most of the land is
under the plough, at least half the plants may be chosen from
among arable weeds, and the balance from hedgebank and
wayside plants. But if any areas of comparatively natural
vegetation exist in the neighbourhood, such as heath, common
or down, then dominant or characteristic plants from these
should certainly be included in the list.
Everything possible should be ascertained about the species
chosen, including as many as may be of the following points :
life-form, i.e. mode of perennation, depth at which the roots
are mainly developed, general structure of shoot system,
vegetative propagation ; any soil preferences or other habitat
preferences that may be observed, time of coming into flower,
duration of flower, structure of flower, mode of pollination,1
whether seed is set and ripened, and if so how much; relations
to other plants (competition, etc.). This will be a sufficient
programme for the summer term, and if the children are
very young, it will have to be considerably simplified, for
* This is hy no means always easy to determine. The simple
experiment of tying a muslin bag over the flowers will show whether
large insects are necessary, but small insects (e.g. Thrips) can crawl
through most muslins. T?he muslin may also, in a wet season, inter-
fere with evaporation sufficiently to cause the flower to rot, Never-
theless the attempt should be made.